Bone screw

ABSTRACT

A bone screw is created, with a thread section ( 1 ) with a tip ( 6 ) at a first end and a head ( 8 ) for engaging with a screwdriver at the opposite second end, which serves as traction element to connect shattered or split off parts of bones to one another. So that fusion of the screw with the bones can take place, the thread section ( 1 ) is constructed as tubular and its wall has a plurality of recesses.

The invention relates to a bone screw with a thread section, a tip on afirst end and a head for engaging with a screwdriver at the oppositesecond end.

From EP-A-0 682 917 a hollow cylindrical pin is known, which has anouter bone thread, beginning at a distance from its tip, and alsorecesses in its outer casing to enable bone integration. The device isconstructed in such a way that screwing in is possible only into adrilled hole, which has to be made beforehand.

From WO 97/37603 a bone screw is known, the shank of which has aplurality of perforations, made by drilling, for growing in.

From U.S. Pat. No. 6,048,343 a bone screw system with a chamfered bonescrew is known.

The object of the invention is to improve a bone screw of the kindinitially described.

This object is achieved by a bone screw in which the tubular threadsection has a bone thread on its outer wall and at least at one end aninner thread section for screwing in the head or tip. This producesgreat variability, as various heads or tips can be screwed in.

According to a further development the inner thread extends over theentire length of the thread section. In this way the advantage isachieved that the thread section can be shortened in situ to any desiredlength, so here too variability is increased.

According to another solution the bone screw is characterised in thatthe tubular thread section has a bone thread on its outer wall and thetip is constructed as a self-cutting tip. This does away with thenecessity of first making a bore to accommodate the screw. A furthersolution is characterised in that the tubular thread section has a bonethread on its outer wall and the head and/or the tip are so dimensionedthat they can be inserted to fit snugly into the ends of the threadsection. Here again the variability of ways of insertion is increased ifthe thread section can be shortened in situ to a desired length and thenhead or tip of the desired kind can be inserted.

Further developments of the invention are characterised in thesubordinate claims.

Further features and advantages of the invention emerge from thedescription of embodiment examples using the figures.

FIG. 1 shows an exploded illustration.

FIG. 2 shows a compiled screw of a first embodiment.

FIG. 3 shows a compiled screw of a second embodiment.

FIG. 4 shows a detail from FIG. 1 in enlarged scale.

FIG. 5 shows a detail from FIG. 1 in section in enlarged scale.

As can best be seen from FIG. 1, the bone screw has a tubular threadsection 1. This has in its wall a multiplicity of recesses 2, which inthe embodiment example shown are constructed as lozenge-shaped.Alignment of the lozenges therein takes place in such a way that in eachcase one symmetrical axis extends parallel to the symmetrical axis ofthe tube. A first set of recesses 2 is offset from one another in thecircumferential direction. Adjacent, seen in the axial direction, therefollows a further set of recesses 3, which seen in the circumferentialdirection are at the same distance, but are so arranged that in eachcase, seen in the axial direction, an orifice of the second set 3 liesbetween two orifices of the preceding set 2. The pattern continues overthe entire surface. Although the orifices are preferably constructed aslozenge-shaped, according to other embodiment examples other forms oforifice, in particular round orifices, can be provided.

On the outer wall a so-called bone thread 4 is provided, which in shapecorresponds to the normal bone screws. The bone thread is shown indetail in FIG. 4.

The bone screw further comprises a tip 6 attached to one end of thetube. The tip comprises the actual tip part and a shank 7. In theembodiment example shown the shank 7 has a metric outer thread. Thetubular thread section 1 has on its inner wall a corresponding metricinner thread and the tip and the tube are rigidly connected to oneanother by screwing in the tip in the way which can be seen in FIG. 2.The two metric threads are therein constructed as left threads againstthe right thread inclination of the bone thread 4.

The bone screw further comprises a head 8, which, as can best be seenfrom FIG. 1, has the actual head part 9 with a slit or an inner hexagonand a thread shank 11. The tube forming the thread section 1 has on itsassociated end a metric inner thread which matches the thread of thethread shank 11. The two cooperating threads of the thread shank 11 andthe inner thread are also preferably constructed as left threads. Thehead 8 is rigidly screwed into the thread section 1 in the way shown inFIG. 2.

The embodiment shown in FIG. 3 differs from the first describedembodiment in that the tip 12 is constructed as a self-cutting tip. Inthis embodiment and also in the first embodiment the tips are roundedoff in each case in the way shown in the figures.

In the above-described embodiments the tip and the head are screwed in.The metric inner thread extends in each case over the two ends in such away that head and tip can be screwed in.

According to a preferred embodiment the inner thread extends over theentire length of the thread section. This has the advantage that thetube can be cut to any length, so screws of desired length can beproduced, so storage can be considerably reduced.

According to an alternative embodiment the inner wall of the threadsection 1 and the respective shanks 7 and 11 are constructed without therespective threads and defined in their measurements in such a way thattip and head are rigidly connected to fit snugly to the thread section1.

Alternatively a thread can be provided at one end and the associatedelement, in other words tip or head, can have a corresponding thread andbe able to be screwed in, so at this end cutting the tube to apredetermined length remains possible, and the other element, in otherwords head or tip, can be attached to fit snugly.

The parts forming the bone screw are preferably made of titanium.

The possibility of screwing in tip and head also creates the advantagethat bone material or some other growth-promoting material can be filledinto the cavity of the thus formed screw, thus greatly accelerating thehealing process.

1-8. (canceled)
 9. A bone screw comprising a tubular section with twoends, a head at one end and a tip at an opposite end, the tubularsection having a wall with a plurality of recesses, the wall furthercomprising an exterior bone thread and an interior thread section forengagement with at least one of the head and the tip.
 10. The bone screwaccording to claim 9, wherein the tip comprises a self-cutting tip. 11.The bone screw according to claim 9, wherein the inner thread sectioncomprises a metric thread.
 12. The bone screw according to claim 11,wherein the tip comprises a self-cutting tip.
 13. The bone screwaccording to claim 9, wherein the inner thread extends over the entirelength of the tubular section.
 14. A bone screw comprising a tubularsection with two ends, a self-cutting tip at a first end a head forengaging with a screwdriver at an opposite end, the tubular sectionhaving a wall with a plurality of recesses, the wall further comprisingan exterior bone thread.
 15. The bone screw according to claim 14,wherein at least at one end of the tubular section has an interiorthread section for engagement with at least one of the head and the tip.16. A bone screw comprising a tubular section with two ends, a tip at afirst end a head for engaging with a screwdriver at an opposite end, thetubular section having a wall with a plurality of recesses, the wallfurther comprising an exterior bone thread, at least one of the head orthe tip being structured and arranged to fit snugly into an end of thetubular section.
 17. A bone screw according to claim 16, wherein the tipcomprises a self-cutting tip.